Powertrain, generic (extended)

P2BBB Turbocharger/Supercharger Bypass Valve A Position Sensor Circuit

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modePossible

P2BBB is the general fault of the position feedback from bypass valve A, the electrically driven valve that lets boosted air flow back from the compressor outlet to its inlet when the throttle closes or boost has to be trimmed. It is not the wastegate on the exhaust side. The engine module reads the sensor as a share of its 5 V reference; this code covers an open line or a signal it cannot sort into low or high. GM's 2019 tables for the supercharged 6.2-litre LT5 (Corvette ZR1) watch this sensor but publish only the low and high codes P2BBC and P2BBD; no manufacturer documents P2BBB itself publicly. An Achates Power patent explains why the feedback matters: without a valid position the commanded opening cannot be verified and boost control loses accuracy. Expect a warning light and reduced boost.

Likely causes

Loose, corroded or unplugged connector at the bypass valve position sensor

Chafed or broken signal, reference or ground wire in the harness near the compressor

Internal fault of the position sensor in the valve actuator

Faulty sensor input or 5 V reference inside the engine control module

Symptoms

Check engine light
Reduced boost and noticeably less power
Whoosh or flutter noise when lifting off the throttle

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€60–900

Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

turbo bypass valve awiring harnessecm

References: law.cornell.edu, gsi.ext.gm.com, patents.google.com.